In certain rigorous workplace environments and situations, it has been found that chain saw cutter bar-detachable nose constructions available on the market are prone to bending, distortion and even permanent damage. This can occur in a tree falling accident, or when a cut tree sets back on the saw bar, or when the chain saw bucks excessively or is subjected to extremely rough handling. The chain saw cutter bar-detachable nose design disclosed in U.S. Pat. No. 3,762,047, Dennis G. Scott-Jackson, Oct. 2, 1973, represented an important and valuable advance in the chain saw art and because of this, it has over the years received broad world-wide acceptance and commercial success. However, to discuss the Scott-Jackson design in particular, although it is not the only design which is susceptible to bending, it has been found that the cutter bar can become bent along a line extending laterally across the bar at the point where the extensions extend from the bar body to support and engage with the end sprocket. The bend between the bar and the nose tends to cause a pinch to the rear side of the sprocket located within the nose. This can cause heat due to friction, softening of the sprocket and possibly breakage of the sprocket, nose or bar. In another instance, particularly where the chain saw and cutter bar are subjected to very rough treatment or tough cutting jobs, or where bending at the nose extensions takes place, the extensions of the bar can become slightly spread. In extreme cases, one or more of the bar extensions may become permanently bent or even break off. Thus, the bar must be replaced.
Other chain saw cutter bar-nose designs currently available on the marketplace are also prone to bending problems, some more serious than the Scott-Jackson design.
The applicant is aware of the following references which may have some relevance to the applicant's novel bar-nose design:
______________________________________ U.S. Pat. No. Issue Date Inventor ______________________________________ 2,316,997 April 20, 1943 Smith 3,762,047 October 2, 1973 Scott-Jackson 3,955,279 May 11, 1976 Pierson 3,987,544 October 26, 1976 Gibson 4,021,913 May 10, 1977 Arff 4,060,895 December 6, 1977 Hille 4,259,783 April 7, 1981 Scott-Jackson et al. 4,489,493 December 25, 1984 Tsumura ______________________________________
These references illustrate various designs and constructions of internal cutter bar-spacer plate assemblies. Many of the designs are prone to bending problems. None discloses or teaches the applicant's invention whereby calculated points of varying strength are custom built into the cutter bar-nose bar assembly to thereby encourage bending at certain preferential locations. This action reduces pinching of the sprocket in the nose of the cutter bar-nose assembly. The references also do not disclose the utilization of a solid web between the nose extensions to prevent lateral spreading of the extensions of the bar on either side of the nose extensions.